Mixed Revision Questions and Answers

Combined Science Questions (Page 1)

Mixed Revision Questions and Answers (Page 1)

Question 1

Use the table below to answer the questions that follow:

SubstancepH
A1
B5
C7
D9
E14

a) Which substance is a weak alkali?
b) Which substance could be water?
c) Which substance is a weak acid?
d) Which substance could result from the neutralisation of an acid and an alkali?
e) Which substance could neutralise A?
f) Which substance could be aqueous sodium hydroxide?
g) Which substance could be dilute sulphuric acid?

Solution 1

a) D
weak alkalis and weak acids have pH close to 7

b) C
water is a neutral substance. All neutral substances have a pH of 7.

c) B
weak alkalis and weak acids have pH close to 7

d) C
all products of neutralisation are neutral and have a pH of 7

e) E
A is a strong acid since it has a pH of 1. E is the substance that could neutralise A because E is a strong alkali since it has a pH of 14.

f) E
The greater the pH, the greater the alkalinity of a substance.

g) A
A has the lowest pH which corresponds to a strong acid like sulphuric acid.

Read more about Acids, Bases and Salts



Question 2

Sodium sulphate can be obtained from sulphuric acid and sodium hydroxide by a titration method.
a) What do you understand by the term titration?
b) How would you obtain hydrated sodium sulphate crystals from an aqueous solution of sodium sulphate?
c) Using only dilute sulphuric acid, how would you distinguish between a solution of zinc nitrate and a solution of barium nitrate?
d) Sulphuric acid is said to be a strong acid and its molecule is dibasic. Explain what this means.

Solution 2

a) Titration is a volumetric analysis method used to measure the concentration of one substance by slowly adding it to a substance of known concentration until an end-point is reached.

b) by heating the solution until we get a saturated solution and then leaving it open for a few days to crystallise.

c) Dissolve zinc nitrate and barium nitrate in separate beakers of dilute sulphuric acid. Barium nitrate will form a white precipitate of barium sulphate.

d) When in aqueous solution, sulphuric acid completely dissociates, each mole of sulphuric acid producing two moles of H+ ions.
A strong acid is an acid that completely dissociates in water to produce H+ ions whilst a weak acid is an acid that partially dissociates in water to produce H+ ions. One mole of a monobasic acid produces one mole of H+ ions, One mole of a dibasic acid produces two moles of H+ ions, One mole of a tribasic acid produces three moles of H+ ions. Hydrochloric acid is monobasic, sulphuric acid is dibasic, phosphoric acid is tribasic.



Question 3

Germanium is a white, shiny, brittle element. It is used in the electronics industry because it is able to conduct a small amount of electricity. It is made from germanium oxide obtained from flue dusts of zinc and lead smelters. The impure germanium oxide from the flue dusts is changed into pure germanium by the process outlined below.

  1. The germanium oxide is reacted with hydrochloric acid to make germanium tetrachloride. This is a volatile liquid in which the germanium and chloride atoms are joined by covalent bonds.
  2. The germanium tetrachloride is distilled off from the mixture.
  3. The germanium tetrachloride is added to an excess of water to produce germanium oxide and hydrochloric acid. Step 1 to 3 are repeated several times.
  4. The pure germanium oxide is reduced by hydrogen to form germanium

a) Write a balanced equation to represent step 1 above.
b) Write a balanced equation for the reaction in step 3.
c) Suggest why steps 1 to 3 are repeated several times.
d)The equation which represents the reactions in Step 4 is shown below:

GeO2 + 2H2 → Ge + 2H20
i) Explain what is meant by the term ‘reduced’.
ii) Calculate the mass of germanium which could be made from 525g of germanium oxide(Relative atomic masses : Ge = 73; O = 16)
e) Germanium is difficult to classify as either a metal or a non metal.
(i)Give evidence from the information in this question to show that germanium is a metal.
(ii)Give evidence from the information to show that germanium is a nonmetal.

Solution 3

a) GeO2(s) + 4HCl(aq) → GeCl4(aq) + 2H2O(l)
tetra means 4 hence Germanium tetrachloride has 4 chlorine atoms.

b) GeCl4(aq) + 2H2O(l) → GeO2(s) + 4HCl(aq)

c) To make sure that all germanium oxide has been extracted from the impure oxide.

d)i) ‘Reduced’ means the oxygen was removed from the germanium oxide.

ii) Mass of germanium = 73/(73 + 32) × 525
= 73/105 × 525
= 365g

e) i) It is white and shiny.
ii) It is brittle.



Question 4

Choose from the list, the element which bests fits each description in(i) to(iv).

  • Bromine
  • magnesium
  • calcium
  • mercury
  • chlorine
  • nitrogen
  • gold
  • oxygen
  • iodine
  • rubidium

i)This metal is a liquid at room temperature.
ii)This green/yellow gas is used to make bleaches.
iii)This metal reacts quickly with water producing bubbles of hydrogen gas .The element will have similar properties to sodium.
iv)This halogen is a black solid which readily turns into a purple vapour when heated.

Solution 4

i) Mercury
ii) Chlorine
iii) calcium
iv) iodine



Question 5

a)Sodium hydrogencarbonate is present in indigestion powders. It is often called bicarbonate of soda. Sodium hydrogencarbonate:

  • is a white solid
  • does not smell
  • form a solution with a PH of about 8.5
  • is very soluble in water
  • is not poisonous

i)Is sodium hydrogen carbonate solution acidic, alkaline or neutral?
ii) Indigestion can be cause by too much acid in the stomach. Which two pieces of information in the list are the most important reasons why sodium hydrogencarbonate can be used as an indigestion powder?
b) Nitric acid reacts with sodium hydrogencarbonate .The salt formed is a nitrate. Write the word equation for this reaction.
c) Vinegar is sometimes put on chips. It has a sour, sharp taste, What does the taste tell you about vinegar?
d) If you added some washing soda crystals to vinegar what would you see happening?
e) Hydrochloric acid is said to be a strong acid. Explain the meaning of this statement.
f)What are the products of the reaction of an acid and a base?
g) Giving examples, state what you understand by:
i) Electrolyte
ii) Non electrolyte
h) Give the formulae (with charges)of the ions present in solutions of:
(i) Ammonium sulphate
(ii)aluminium(III)chloride
(iii)copper(II)nitrate

Solution 5

a)i) It is alkaline.
because its pH is above 7.

ii) sodium hydrogencarbonate has pH of about 8.5 and it is not poisonous.

b) sodium hydrogencarbonate + nitric acid → sodium nitrate + water + carbon dioxide

c) it is an acid.
acids have a sour taste.

d) A fizzy reaction producing bubbles of carbon dioxide.

e) It completely dissociates in water to produce hydrogen ions as the only positively charged ions.

f) Salt and Water

g) i) An electrolyte is a substance that conducts electricity either in solution or in molten state due to the movement of ions.
Examples are molten lead bromide and dilute sulphuric acid.

ii) A non electrolyte is a substance that does not conduct electricity either in solution or in molten state.
Examples are sucrose and kerosene.

h) i) Ammonium sulphate – NH4+ and SO42+

ii) Aluminium(III) chloride – Al3+ and Cl

iii) Copper(II) nitrate – Cu2+ and NO3

Question 6

Complete the following account in the manufacture of ammonia by writing the missing word and by giving the equation for the reaction.
(i)Ammonia is manufactured by the direct combination of nitrogen and hydrogen, a reaction known as…………………………
The equation for the reaction is …………………….
(ii)The nitrogen is obtained by the fractional distillation of liquid…………………………
(iii)The nitrogen and hydrogen are compressed to ……………….. and react at 500 degrees Celsius to 550 degrees Celsius in the presence of ………………….. which acts as a catalyst.
(iv)Under high pressure the ammonia liquefies and the unreacted nitrogen and hydrogen are ………….

Solution 6

(i) Haber process
N2 + 3H2 → 2NH3

(ii) air

(iii) 200 atmospheres
iron

(iv) recycled.

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